To meet the demand for wireless data traffic having increased since deployment of 4G (4th-Generation) communication systems, efforts have been made to develop an improved 5G (5th-Generation) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’. The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like. In the 5G system, Hybrid FSK and QAM Modulation (FOAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of Things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of the IoT technology and the Big Data processing technology through connection with a cloud server, has emerged. As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “Security technology” have been demanded for IoT implementation, a sensor network, a Machine-to-Machine (M2M) communication, Machine Type Communication (MTC), and so forth have been recently researched. Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing Information Technology (IT) and various industrial applications.
In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as a sensor network, Machine Type Communication (MTC), and Machine-to-Machine (M2M) communication may be implemented by beamforming, MIMO, and array antennas. Application of a cloud Radio Access Network (RAN) as the above-described Big Data processing technology may also be considered to be as an example of convergence between the 5G technology and the IoT technology.
In general, a communication system has a multi-cell structure, and the configuration and use of transmission/reception beams in a multi-cell communication system act as important factors that influence an overall system capability of the multi-cell communication system.
In the multi-cell communication system, a multi-Base Station (BS) access model, in which a plurality of User Equipments (UEs) sequentially or simultaneously receive services from a plurality of base stations according to a movement speed or communication quality, is considered to provide a seamless service and high quality communication to each UE. However, a communication method of the UE through a multi-beam service of multiple BSs has not been researched in earnest, and most conventional technologies used frequency resources and time resources instead of efficiently using transmission/reception beams or simply concentrated on performance improvement through simultaneous services of multiple BSs. When the BS determines whether to allow multiple accesses based on the use of transmission beams, the range of adjacent BSs with which each BS shares information on whether to use the beams is not clear, and, in order to use the transmission beams, information should be updated between all adjacent BSs whenever a change in the UE is made. Representative methods of the technologies for the conventional multi-BS multi-user service include a multi-access channel and a frequency hopping scheme.
FIG. 1 schematically illustrates a multi-access channel scheme used in a general multi-cell communication system.
Referring to FIG. 1, the multi-access channel scheme includes a plurality of Base Stations (BSs) (two BSs 111 and 113 are illustrated in FIG. 1) and one UE 115. A multi-access channel corresponds to a model in which a plurality of BSs simultaneously access one UE, and FIG. 1 is only an example and the multi-access channel is applied to two or more BSs and a UE.
In FIG. 1, when BS #1 111 and BS #2 113 configure transmission beam #1 117 and transmission beam #2 119, respectively, and simultaneously transmit the transmission beams to UE #1 115, UE #1 115 configures reception beams of various directions and forms according to directions and forms of the transmission beams. FIG. 1 illustrates four types of reception beams, that is, reception beam #1 121, reception beam #2 123, reception beam #3 125, and reception beam #4 127 as an example of the reception beams configured by UE #1 115.
The multi-access channel has a problem that the UE 115 should alternately use reception beam #1 121, reception beam #2 123, reception beam #3 125, and reception beam #4 127 according to time and thus form different reception beams according to time or frequency resources as illustrated in an example of FIG. 1. Further, since the form of a reception beam which can be formed has a limitation due to a physical limit of the UE 115, the number of BSs that can simultaneously provide services to the UE 115 is limited compared to the number of BSs which can actually provide the services. In addition, transmission beam information of BSs that access the UE 115 should be shared with the UE 115 every time, and the UE 115 should inform all neighboring BSs every time of information on reception beams formed based on the transmission beam information and whether to maintain the multi-access channel with the corresponding BSs.
FIG. 2 illustrates an example of a frequency hopping scheme used in the general multi-cell communication system.
The frequency hopping scheme corresponds to a scheme that uses the whole frequency in predetermined divided time intervals. Since one frequency resource is used only for a predetermined time and another frequency resource is used for another predetermined time in the frequency hopping, it is possible to reduce influence of interference from an interferer that uses the same frequency resource. However, the whole frequency band allocated to the UE cannot be used at the same time, thereby deteriorating the performance. Further, since a new beam should be formed according to each frequency resource, pieces of transmission and reception beam information, which should be shared between all neighboring BSs and all UEs, become larger as the frequency hopping is implemented through a plurality of frequency resources.
Particularly, in a communication model using a high frequency bandwidth, which is currently spotlighted as a next generation communication model, a scattering effect of reception signals to be used for communication becomes weak according to a movement of the UE or a regional characteristic. However, the frequency hopping scheme cannot solve the problem of the weakness of the scattering effect, but rather worsens the problem, so it is difficult to apply the frequency hopping scheme to the next generation mobile communication model.
Since BSs for a multi-access service is limited according to a physical limitation in forming reception beams and an amount of information exchanged between the BS and the UE is large in a communication model using a multi-access channel scheme and a high frequency bandwidth, it is not possible to provide a service having stable performance which the UE desires to acquire.